The invention relates generally to devices that read optically encoded information. More specifically, the invention relates to a device for reading optically encoded information from the edge of a strip of photographic film.
Many photographic films are identified by an optical bar code that is part of an industry standard "DX" film identification system. The DX coding includes information related to the film sensitivity and is printed in the form of a latent image on an edge of a negative film. The DX bar code includes a clock track and a data track, both of which must be read and correlated in order to decode the information contained therein.
There are a number of difficulties associated with attempting to design a simple and inexpensive DX bar code reader. For example, standard optical devices are larger than the track spacing of the clock and data tracks, the optical density of the "on" and "off" regions of the tracks varies among film types and film treatment, the pitch of the code varies among film types, the position of the code with respect to the edge of the film varies, and the film must be read while it is moving through a film gate assembly. The above difficulties have resulted in bulky and expensive readers that generally require the use of custom optical devices and/or optical projection to separate the tracks and capture the encoded information.
In view of the above, it is an object of the present invention to provide an inexpensive and compact bar code reader that does not require custom optical devices or optical projection to separate the clock and data tracks of a DX bar code.